Generally, a ringback tone service is a service for transmitting a sound chosen by a called party to a calling party while the calling party waits for the call to be answered by the called party. Such a ringback tone service allows mobile communication subscribers to feel auditory satisfaction and satisfies the mobile communication subscribers' desires to express their personalities by allowing the calling party to hear a specific sound instead of a uniform and mechanical ringback tone.
However, the original ringback tone service, enabling simple music or a voice message to be used as a ringback tone, does not satisfy video call subscribers' desires, and thus a multimedia ringback tone service, enabling video call subscribers to view multimedia content during the call waiting time, has been proposed.
As shown in FIG. 1, a conventional system for providing a Multimedia Ringback Tone (MRBT) service has a network configuration in which an MRBT Intelligent Peripheral (IP) 13 is connected to the Mobile Switching Centers (MSCs) 12 and 12′ of a Wideband Code Division Multiple Access (WCDMA) system, which includes base station/control stations (Node B/Radio Network Controller: RNC) 11 and 11′ and the MSCs 12 and 12′, and an MRBT server 14 is connected to the MRBT IP 13. The call processing procedure for the MRBT service will be described below with reference to FIG. 2.
As shown in FIG. 2, when an Originating mobile terminal (Mobile Station: O_MS) transmits a setup message required to establish a 3G-324M protocol as a calling subscriber requests a video call at step S201, an Originating MSC (O_MSC) requests the location information (Send Routing Information: SRI) of a terminating MS (T_MS) from a Home Location Register (HLR) at step S202. The HLR requests Provide Routing Number (PRN) information from a terminating MSC (T_MSC) at step S203, and receives the PRN information at step S204. Thereafter, the HLR provides Send Routing Information (SRI), detected using the PRN information received from the terminating MSC (T_MSC), to the originating MSC (O_MSC) at step S205.
The originating MSC (O_MSC), having received the SRI, transmits an Initial Address Message (IAM), including the identification information of the terminating MS, to the T_MSC, thus requesting the setup of a circuit from the T_MSC at step S206. The terminating MSC (T_MSC) transmits an Address Complete Message (ACM) to the originating MSC (O_MSC) so as to establish a traffic channel between the originating MSC (O_MSC) and the terminating MSC (T_MSC) at step S207. At the same time, the T_MSC transmits an IAM, including the identification information (phone number) of the originating MS, to the MRBT_IP at step S209.
After the MRBT_IP, having received the IAM, transmits an Address Complete Message (ACM) to the T_MSC at step S210, the MRBT_IP requests a sound source code, registered by the called party, from the MRBT server at step S211. When receiving a relevant sound source code at step S212, the MRBT_IP establishes a channel through the negotiation of resources based on an H.245 protocol so as to establish a channel with the originating MS (O_MS) at step S214.
Meanwhile, the originating MSC (O_MSC), having received the ACM at step S207, transmits an alert message (Alert) to the originating MS (O_MS) at step S208. The originating MS (O_MS), having received the alert message, negotiates with the terminating side about the establishment of audio and video channels and the setup of a codec based on the H.245 protocol at step S213. When channels have been established as a result of the negotiation, the terminating MSC (T_MSC) provides stored multimedia content to the originating MS (O_MS) at step S215.
Meanwhile, when paging/paging response between the terminating MSC (T_MSC) and the terminating MS (T_MS) is performed at steps S216 and S217, the terminating MSC (T-MSC) transmits a setup message to the terminating MS (T_MS) at step S218. After the terminating MS (T_MS) transmits a call confirmed message (Call Confirmed) and an alert message (Alert) to the terminating MSC (T_MSC) at steps S219 and S220, the T_MS determines a codec and establishes a channel based on the H.245 protocol, together with the terminating MSC (T_MSC), in response to the setup message at step S221, and communicates with the T_MSC based on an H.223 protocol at step S222.
Next, when the user answers the incoming call, the terminating MS (T_MS) transmits a connect message (Connect) to the T_MSC at step S223. The T_MSC, having received the connect message, transmits an Answer Message (ANM) to the originating MSC (O_MSC) at step S224, and thereafter transmits a response to the connect message to the terminating MS (T_MS) at step S225. Further, the originating MSC (O_MSC) and the terminating MSC (T_MSC) perform operations, required to release the transmission of multimedia content that is currently being provided, at steps S226, S227, and S228, and notify the originating MS (O_MS) of the connection with the terminating MS at step S229. When receiving a connect response at step S230, the originating and terminating MSs perform video call communication.
Meanwhile, as described above, since the multimedia ringback tone service based on a WCDMA network, proposed in the prior art, is a circuit network-based service in which the MRBT_IP plays multimedia content through the mobile switching center, the conventional MRBT service can be provided only to a video call terminal, that is, a terminal supporting protocols for a video call and a codec related thereto, but cannot be provided to a voice call terminal for transmitting a typical voice call over the WCDMA network.
Further, when a conventional circuit network-based MRBT service is intended to be applied to a typical voice call terminal, the function of enabling the terminal to use a channel for a video call must be added to the terminal, and thus the implementation of the MRBT service in the voice call terminal is difficult. Moreover, since multimedia content, which requires a wide bandwidth, cannot be transmitted through a typical voice call channel, which has a narrow bandwidth, the conventional circuit network-based MRBT is not suitable for typical voice call subscribers.
Furthermore, since the conventional circuit network-based MRBT service employs a method in which an MRBT_IP plays multimedia content, there is a problem in that a channel required to play the multimedia content must be occupied while the multimedia content is played, thus wasting channel resources.
In addition, most mobile communication subscribers mainly call several designated persons. However, the conventional multimedia ringback tone service is problematic in that, since the MRBT_IP merely plays multimedia content each time, but is not operated to separately store the multimedia content in a mobile communication terminal, a calling party must be provided with the same multimedia content that was played the previous time, occupying channel resources every time a call is made, thus resulting in the serious waste of channel resources.
As a result, a method of more efficiently processing a multimedia ringback tone service is urgently required, and the activation of WCDMA service has recently been conducted in earnest, so that a detailed multimedia ringback tone service method applicable to a WCDMA system is urgently required.